Here's a place where I can post my thoughts on new papers, provide updates on my projects, and post info that will eventually be on my website The Theropod Database - http://theropoddatabase.com/ . It will center on theropods, but may delve into other topics as well such as phylogenetics.

Thursday, August 22, 2019

Therizinosaurs in the Lori matrix

Next up are therizinosaurs. These are one of the best analyzed clades because I incorporated all of Zanno's (2010) characters, which is by far the largest and most recent analysis of the group until the Lori paper was published. The topology is-

Falcarius is the most basal taxon shown of course, but Martharaptor was pruned a posteriori and can fall out anywhere in Therizinosauria outside the Alxasaurus plus Segnosaurus clade. I tried including Thecocoelurus, but the Lori matrix is pretty terrible when it comes to scoring single vertebrae-

Jianchangosaurus fell out in the same place as its original description, with Cau's (2018) placement in Alvarezsauroidea taking 18 more steps so is very unlikely. Mine is the only published matrix besides Senter (2011) and its derivatives to use information from the second Beipaiosaurus specimen, and incorporated photos from Zanno and the new paper on the holotype skull elements too.

Zanno also provided photos of Alxasaurus and Enigmosaurus, and its depressing how much of the former is lost. Enigmosaurus rather famously was shown by Zanno to not resemble Barsbold's original illustration that was the only reference picture known for over two decades. Placing Enigmosaurus closer to Segnosaurus than Neimongosaurus or Erliansaurus as in Zanno's tree takes 4 more steps. Forcing Enigmosaurus and Erlikosaurus to be sister taxa to simulate the synonymy mentioned by Barsbold (1983) takes 4 steps, so seems unlikely. The duo moves between Nanshiungosaurus and the Segnosaurus plus Nothronychus clade. We were the first analysis to include "Chilantaisaurus" zheziangensis, which emerged in a polytomy with Alxasaurus, Enigmosaurus and therizinosaurids.

As was the case with Archaeornithomimus? bissektensis, we didn't include the possible chimaera of Bissekty Therizinosauria as an OTU, unlike Sues and Averianov (2015). But if you do want to experiment with it, here's the scorings. It emerges in a polytomy in the Suzhousaurus plus Therizinosaurus clade of therizinosaurids. Btw, Archaeornithomimus? bissektensis does fall out most parsimoniously sister to A. asiaticus when all Bissekty material is used.

Next is Therizinosauridae itself, which we refined Zhang et al.'s (2001) definition of to include type species. Therizinosaurids first split into a clade of Erliansaurus, Neimongosaurus, Suzhousaurus and Therizinosaurus. Forcing the former two to be outside a clade of Suzhousaurus, Therizinosaurus and the taxa below, as in Zanno's tree, takes 5 more steps. Notably, we did not include the hindlimb IGM 100/45 in the Therizinosaurus OTU since there's no overlap and its not even particularly large. But here's the Therizinosaurus OTU including the hindlimb. Using this version of Therizinosaurus leaves the tree basically the same but destabilizes it somewhat in that Therizinosaurus and Erlikosaurus can now go in multiple positions within Therizinosauridae, and the Nanchao embryos are in a trichotomy with the Suzhousaurus clade and the Nothronychus clade. Is this an indication the hindlimb produces homoplasy and so might not belong to Therizinosaurus?

Now comes the Nanchao therizinosaur embryos, those described by Kundrat et al. inside dendroolithid eggs. While including such young specimens might be seen as risky, my ontogenetically conservative scoring method with state N seems to have worked fine here. They fall out where you'd expect a Santonian-Campanian therizinosaur to do so. Following that is Nanshiungosaurus brevispinus, which Senter et al. (2012) recovered as the next most derived therizinosaur after Alxasaurus. Forcing it into this basal position takes 4 steps. Nanshiungosaurus? bohlini was included but pruned a posteriori since it can go anywhere in the Segnosaurus plus Nothronychus clade. Forcing Nanshiungosaurus monophyly is just a single step longer though, while forcing bohlini to be sister to the contemporaneous Suzhousaurus takes 2 steps.

Segnosaurus itself (which Zanno also provided photos of) pairs with ex-Alectrosaurus forelimb AMNH 6368, which has only previously been analyzed by Zanno (2006) where it pairs with Erliansaurus. Forcing that here compared to other taxa she included results in trees 3 steps longer. Erlikosaurus groups with the Nothronychus species in a trichotomy where it can be sister to either species. Forcing Nothronychus monophyly takes only a single step, but note that no proposed Nothronychus characters involve elements that can be compared to Erlikosaurus (humerus and pes). Forcing Erlikosaurus to group with Therizinosaurus as in Senter et al. requires only a single step, with Erlikosaurus moving to the Therizinosaurus clade.

Hartman, Mortimer, Wahl, Lomax, Lippincott and Lovelace, 2019. A new
paravian dinosaur from the Late Jurassic of North America supports a
late acquisition of avian flight. PeerJ. 7:e7247. DOI: 10.7717/peerj.7247